1. Field of the Invention
The present invention relates to an apparatus for processing image information.
2. Related Background Art
Conventional image processing apparatus have been very expensive, and large in size, and require a long processing time, so that they could only be used as printing systems. Examples of such expensive apparatus are the Response 300 series manufactured by Scitex, and the Studio-800 series manufactured by Crosfield.
In general an image editing apparatus requires two editing functions:
1. high-speed processing with a hardware circuit; and
2. software processing with a CPU.
The former is achieved by hardware generally called a pipeline processor, and is applied to certain items of image processing requiring a high speed. On the other hand, the latter process with a CPU is applied to certain items conducted in an interactive manner with the operator, with a certain processing time.
More specifically, said pipeline processor is principally applied to successive image processing, such as affine conversion (enlargement, reduction, displacement or rotation) for determining the image layout, spatial filtration (image enhancement or smoothing) and color conversions with a look-up table.
On the other hand, the latter CPU processing is generally applied to complex processes or those which cannot be easily implemented as hardware. More specifically there are included extraction of an image of an arbitrary shape, copying of a thus extracted image to another location, and a partial correction of an image. These processes generally require creativity of the operator and can tolerate a certain processing time, but this processing function is required to be highly advanced.
The image editing apparatus should be designed from its system architecture, in order to achieve the above-mentioned two editing functions with maximum performance. More specifically, in order to achieve these functions satisfactorily with a high speed, it is necessary to consider the structure of the system, the data format to be handled, the flow of signals, the construction of functions, etc.
Various investigations have led to the following features as the system architecture of a color image processing apparatus:
(1) For achieving image processing, the image data should be maintained as compressed data; PA1 (2) For signal compression is preferred a vector quantization in which an m.times.m block is represented by a code; and PA1 (3) Hardware processing is most reasonably conducted as a successive processing upon signal transfer in signal reading, for example from a rigid disk.
With respect to (1), image editing processing with a high resolving power and a high tonal rendition requires an enormous memory capacity. As an example, if a page of A4-sized color image is read with a resolving power of 16 pel/mm, there is required a data capacity of ca. 48 Mbyte for three colors of red, green and blue. For achieving the above-mentioned interactive image processing in satisfactory manner, it is important to compress such color image data into a form suitable for processing. For this purpose the vector quantization, mentioned in (2), has been concluded to be optimum.
In a high-speed hardware processing mentioned in (3), a longer processing time will be required if the processing is conducted in two steps, i.e. a transfer step of the data from a file such as a rigid disk to a memory and a processing step for hardware-processing data stored in the memory. On the other hand, a higher speed in processing will become possible if the processing is conducted simultaneously with the transfer step.